1. Field of the Invention
This invention generally pertains to engine starters and more particularly relates to starters for engines having an accessory driven by the engine.
2. Description of the Prior Art
It is common practice to have the engine of a motor vehicle drive accessories, such as air conditioning compressors and electric generators, when the engine reaches its operating speed. In the prior art, some elements of the engine starter gearing are used to drive the accessories instead of having a gear system located between the starter and accessory dedicated solely to driving the starter. A system of this type, described in U.S. Pat. No. 4,572,281, power developed at the input gear of a first gear stage drives the input gear of a second gear stage, which causes an output drive member coupled to the engine to start the engine. When the engine reaches its operating speed, the power input to the first stage declines but the engine continues to drive the output drive member of the second gear stage which drives an accessory shaft. In this arrangement, the second gear stage of the starter works to start the engine and drive the accessory shaft.
A three-phase accessory drive, described in U.S. Pat. No. 4,265,135, produces a high drive ratio over a low speed engine range, a constant speed over an intermediate speed range, and a low drive ratio over a range of engine speeds greater than the intermediate range. This drive system includes a planetary gear set, a friction brake, a one-way clutch and a hydraulic system. The planet gears are driven from the engine crankshaft, the ring gear is connected by pulleys to the accessories and the sun gear is connected to the friction brake. The hydraulic system includes an orifice controlled by a bimetallic element and a pump driven by the ring gear so that the fluid pressure varies with engine speed in a cylinder whose piston is connected to the brake caliper. The brake holds the sun gear stationary and the speed of the accessory pulley mounted on the ring gear increases linearly with engine speed. When the speed of the ring gear increases to a first predetermined speed, fluid pressure increases more rapidly thereby permitting the brake and sun gear to rotate and maintain the ring gear speed constant until the speed of the sun gear reaches that of the carrier. When the sun gear speed exceeds the speed of the carrier, the one-way clutch connects them and the accessory pulleys rotate at the engine speed.